1. Field of the Invention
The present invention relates to a disk storage apparatus in which an actuator positions a record/reproduce head to a target track of a disk-shaped record medium at a high accuracy, and to a technique of inhibiting a track dislocation of the head due to a disturbance such as a vibration and a shock to which the actuator is subject.
2. Description of the Related Art
In a disk storage apparatus for recording information, with the miniaturization and high record density of the apparatus, there has become severe the requirement of a high-accurate positioning of the record/reproduce head to the target track. Particularly a disk storage apparatus mounted on a personal data assistant such as a notebook computer is apt to be subject to a vibration or shock from the outside, thereby affecting largely a head positioning control system.
A disturbance affecting the head positioning accuracy includes a bearing friction of the actuator, an elastic force of a flexible print circuit (FPC) for connecting the actuator with a circuit board, and an inertia force acting on the actuator due to a shock or vibration exerted on the disk storage apparatus from the outside.
Based on a head position signal obtained from servo information having been previously recorded on the disk, there is produced a position error signal indicating a head position error with respect to the target track, whereby the head is positioning controlled so that the position error signal approaches zero. In this case, it may be considered that an external force is estimated by a drive signal of the actuator and the position error signal, and the estimated amount is incorporated into the control system, thereby compensate the external force.
However, the servo information on the disk is discrete one having a certain sampling period, and the head position signal is not a continuous signal. A control band capable of estimating the external force is affected by the sampling frequency, and has an upper limit. As a result, from the drive signal and the position error signal, the external force cannot be correctly estimated, so that the above-mentioned disturbance cannot be negated satisfactorily. That is, the head is difficult to be made to follow correctly the target track.
Particularly, when a vibration or shock exerted on the disk storage apparatus is excessive, only the rotational force developed by the actuator cannot inhibit the disturbance, so that the head is largely dislocated from the target track, whereby the data of the adjacent track can be destroyed. As a method of compensating the dislocation, it can be considered that an acceleration sensor is specially provided, and an acceleration signal detected by the sensor is used for the compensation. However, the provision of the acceleration sensor in the enclosure causes the miniaturization and reduction in price of the apparatus to be hindered.